1. Field of the Invention
The present invention relates to a nitride semiconductor light-emitting device and a method for manufacturing the same.
2. Description of the Related Art
Representative examples of a related art nitride semiconductor light-emitting device include a GaN-based nitride semiconductor light-emitting device.
Referring to FIG. 1, a related art GaN-based nitride semiconductor light-emitting device includes a buffer layer 2, an n-GaN layer 3, an active layer 4, and a p-GaN layer 5, a magnesium-doped InGaN layer 6, and a magnesium-doped GaN layer 7 sequentially stacked on a sapphire substrate or a SiC substrate 1. Insulating layers are formed on the magnesium-doped GaN layer 7 and the n-GaN layer 3, respectively, and a p-electrode 9 and an n-electrode 10 are formed in the corresponding insulating layers, respectively, so that the nitride semiconductor light-emitting device is formed.
Since the buffer layer formed for realizing the related art nitride semiconductor light-emitting device buffers stress between the substrate and a layer grown on the substrate, technology of growing a buffer layer formed of material such as GaN and AlGaN is applied depending on the kind of the substrate such as a SiC substrate and a Si substrate.
However, when the buffer layer is formed of GaN or AlGaN according to the related art, a lattice constant of a material such as GaN and AlGaN is greater than a lattice constant of a substrate such as a sapphire substrate and a SiC substrate and smaller than a lattice constant of a GaN layer formed on the buffer layer. Accordingly, there occurs a problem that a lattice defect such as dislocation and vacancy is generated between the buffer layer and a layer grown on the buffer layer.
Also, there occurs a problem that stress due to thermal impact is caused by a difference of about 35% in a thermal expansion coefficient between the buffer layer and the substrate, or between the buffer layer and the layer grown on the buffer layer.